Manual: openssl-pkeyutl
OPENSSL-PKEYUTL(1SSL) OpenSSL OPENSSL-PKEYUTL(1SSL)
NAME
openssl-pkeyutl - asymmetric key command
SYNOPSIS
openssl pkeyutl [-help] [-in file] [-rawin] [-digest algorithm] [-out file] [-secret file] [-sigfile file] [-inkey
filename|uri] [-keyform DER|PEM|P12|ENGINE] [-passin arg] [-pubin] [-certin] [-rev] [-sign] [-verify]
[-verifyrecover] [-encrypt] [-decrypt] [-derive] [-peerkey file] [-peerform DER|PEM|P12|ENGINE] [-encap] [-decap]
[-kdf algorithm] [-kdflen length] [-kemop mode] [-pkeyopt opt:value] [-pkeyopt_passin opt[:passarg]] [-hexdump]
[-asn1parse] [-engine id] [-engine_impl] [-rand files] [-writerand file] [-provider name] [-provider-path path]
[-provparam [name:]key=value] [-propquery propq] [-config configfile]
DESCRIPTION
This command can be used to perform low-level operations on asymmetric (public or private) keys using any supported
algorithm.
By default the signing operation (see -sign option) is assumed.
OPTIONS
-help
Print out a usage message.
-in filename
This specifies the input filename to read data from or standard input if this option is not specified.
-rawin
This indicates that the signature or verification input data is raw data, which is not hashed by any message
digest algorithm. Except with EdDSA, the user can specify a digest algorithm by using the -digest option. For
signature algorithms like RSA, DSA and ECDSA, the default digest algorithm is SHA256. For SM2, it is SM3.
This option can only be used with -sign and -verify. For EdDSA (the Ed25519 and Ed448 algorithms) this option is
implied since OpenSSL 3.5, and required in earlier versions.
The -digest option implies -rawin since OpenSSL 3.5.
-digest algorithm
This option can only be used with -sign and -verify. It specifies the digest algorithm that is used to hash the
input data before signing or verifying it with the input key. This option could be omitted if the signature
algorithm does not require preprocessing the input through a pluggable hash function before signing (for
instance, EdDSA). If this option is omitted but the signature algorithm requires one and the -rawin option is
given, a default value will be used (see -rawin for details). If this option is present, then the -rawin option
is implied since OpenSSL 3.5, and required in earlier versions.
At this time, HashEdDSA (the ph or "prehash" variant of EdDSA) is not supported, so the -digest option cannot be
used with EdDSA.
-out filename
Specifies the output filename to write to or standard output by default.
-secret filename
Specifies the shared-secret output filename for when performing encapsulation via the -encap option or
decapsulation via the -decap option. The -encap option also produces a separate (public) ciphertext output which
is by default written to standard output, but being binary non-text data, is typically also redirected to a file
selected via the -out option.
-sigfile file
Signature file, required and allowed for -verify operations only.
-inkey filename|uri
The input key, by default it should be a private key.
-keyform DER|PEM|P12|ENGINE
The key format; unspecified by default. See openssl-format-options(1) for details.
-passin arg
The input key password source. For more information about the format of arg see openssl-passphrase-options(1).
-pubin
By default a private key is read from the key input. With this option a public key is read instead. If the
input contains no public key but a private key, its public part is used.
-certin
The input is a certificate containing a public key.
-rev
Reverse the order of the input buffer. This is useful for some libraries (such as CryptoAPI) which represent the
buffer in little-endian format. This cannot be used in conjunction with -rawin.
-sign
Sign the input data and output the signed result. This requires a private key. Using a message digest operation
along with this is recommended, when applicable, see the -rawin and -digest options for details. Otherwise, the
input data given with the -in option is assumed to already be a digest, but this may then require an additional
-pkeyopt "digest:"md in some cases (e.g., RSA with the default PKCS#1 padding mode). Even for other algorithms
like ECDSA, where the additional -pkeyopt option does not affect signature output, it is recommended, as it
enables checking that the input length is consistent with the intended digest.
-verify
Verify the input data against the signature given with the -sigfile option and indicate if the verification
succeeded or failed. The input data given with the -in option is assumed to be a hash value unless the -rawin
option is specified or implied. With raw data, when a digest algorithm is applicable, though it may be inferred
from the signature or take a default value, it should also be specified.
-verifyrecover
Verify the given signature and output the recovered data (signature payload). For example, in case of RSA PKCS#1
the recovered data is the EMSA-PKCS-v1_5 DER encoding of the digest algorithm OID and value as specified in
RFC8017 Section 9.2 .
Note that here the input given with the -in option is not a signature input (as with the -sign and -verify
options) but a signature output value, typically produced using the -sign option.
This option is available only for use with RSA keys.
-encrypt
Encrypt the input data using a public key.
-decrypt
Decrypt the input data using a private key.
-derive
Derive a shared secret using own private (EC)DH key and peer key.
-peerkey file
File containing the peer public or private (EC)DH key to use with the key derivation (agreement) operation. Its
type must match the type of the own private key given with -inkey.
-peerform DER|PEM|P12|ENGINE
The peer key format; unspecified by default. See openssl-format-options(1) for details.
-encap
Use a Key Encapsulation Mechanism (KEM) to encapsulate a shared-secret to a peer's public key. The encapsulated
result (or ciphertext, non-text binary data) is written to standard output by default, or else to the file
specified with -out. The -secret option must also be provided to specify the output file for the derived shared-
secret value generated in the encapsulation process. Encapsulation is supported with a number of public key
algorithms, currently: ML-KEM, X25519, X449, and EC. The ECX and EC algorithms use the RFC9180 DHKEM construction. Encapsulation is also supported with RSA keys via the RSASVE
construction.
At the API level, encapsulation and decapsulation are also supported for a few hybrid ECDHE (no DHKEM) plus ML-
KEM algorithms, but these are intended primarily for use with TLS and should not be used standalone. There are
in any case no standard public and private key formats for the hybrid algorithms, so it is not possible to
provide the required key material.
-decap
Decode an encapsulated secret, with the use of a -private key, to derive the same shared-secret as that obtained
when the secret was encapsulated to the corresponding public key. The encapsulated secret is by default read
from the standard input, or else from the file specified with -in. The derived shared-secret is written to the
file specified with the -secret option, which must also be provided. Decapsulation is supported with a number of
public key algorithms, currently: ML-KEM, X25519, X448, and EC. The ECX and EC algorithms use the RFC9180
DHKEM construction. Decapsulation is also supported with RSA keys via
the RSASVE construction.
-kemop mode
This option is used with the -encap/-decap commands and specifies the KEM mode specific for the key algorithm
when there is no default way to encapsulate and decapsulate shared secrets with the chosen key type. All the
supported algorithms presently support only their default mode, and this option, though available, is not
required.
-kdf algorithm
Use key derivation function algorithm. The supported algorithms are at present TLS1-PRF and HKDF. Note:
additional parameters and the KDF output length will normally have to be set for this to work. See
EVP_PKEY_CTX_set_hkdf_md(3) and EVP_PKEY_CTX_set_tls1_prf_md(3) for the supported string parameters of each
algorithm.
-kdflen length
Set the output length for KDF.
-pkeyopt opt:value
Public key options specified as opt:value. See NOTES below for more details.
-pkeyopt_passin opt[:passarg]
Allows reading a public key option opt from stdin or a password source. If only opt is specified, the user will
be prompted to enter a password on stdin. Alternatively, passarg can be specified which can be any value
supported by openssl-passphrase-options(1).
-hexdump
hex dump the output data.
-asn1parse
Parse the ASN.1 output data to check its DER encoding and print any errors. When combined with the
-verifyrecover option, this may be useful in case an ASN.1 DER-encoded structure had been signed directly
(without hashing it) and when checking a signature in PKCS#1 v1.5 format, which has a DER encoding.
-engine id
See "Engine Options" in openssl(1). This option is deprecated.
-engine_impl
When used with the -engine option, it specifies to also use engine id for crypto operations.
-rand files, -writerand file
See "Random State Options" in openssl(1) for details.
-provider name
-provider-path path
-provparam [name:]key=value
-propquery propq
See "Provider Options" in openssl(1), provider(7), and property(7).
-config configfile
See "Configuration Option" in openssl(1).
NOTES
The operations and options supported vary according to the key algorithm and its implementation. The OpenSSL
operations and options are indicated below.
Unless otherwise mentioned, the -pkeyopt option supports for all public-key types the "digest:"alg argument, which
specifies the digest in use for the signing and verification operations. The value alg should represent a digest
name as used in the EVP_get_digestbyname() function for example sha256. This value is not used to hash the input
data. It is used (by some algorithms) for sanity-checking the lengths of data passed in and for creating the
structures that make up the signature (e.g., DigestInfo in RSASSA PKCS#1 v1.5 signatures).
For instance, if the value of the -pkeyopt option "digest" argument is sha256, the signature or verification input
should be the 32 bytes long binary value of the SHA256 hash function output.
Unless -rawin is used or implied, this command does not hash the input data but rather it will use the data directly
as input to the signature algorithm. Depending on the key type, signature type, and mode of padding, the maximum
sensible lengths of input data differ. With RSA the signed data cannot be longer than the key modulus. In case of
ECDSA and DSA the data should not be longer than the field size, otherwise it will be silently truncated to the field
size. In any event the input size must not be larger than the largest supported digest output size EVP_MAX_MD_SIZE,
which currently is 64 bytes.
RSA ALGORITHM
The RSA algorithm generally supports the encrypt, decrypt, sign, verify and verifyrecover operations. However, some
padding modes support only a subset of these operations. The following additional pkeyopt values are supported:
rsa_padding_mode:mode
This sets the RSA padding mode. Acceptable values for mode are pkcs1 for PKCS#1 padding, none for no padding,
oaep for OAEP mode, x931 for X9.31 mode and pss for PSS.
In PKCS#1 padding, if the message digest is not set, then the supplied data is signed or verified directly
instead of using a DigestInfo structure. If a digest is set, then the DigestInfo structure is used and its length
must correspond to the digest type.
Note, for pkcs1 padding, as a protection against the Bleichenbacher attack, the decryption will not fail in case
of padding check failures. Use none and manual inspection of the decrypted message to verify if the decrypted
value has correct PKCS#1 v1.5 padding.
For oaep mode only encryption and decryption is supported.
For x931 if the digest type is set it is used to format the block data otherwise the first byte is used to
specify the X9.31 digest ID. Sign, verify and verifyrecover are can be performed in this mode.
For pss mode only sign and verify are supported and the digest type must be specified.
rsa_pss_saltlen:len
For pss mode only this option specifies the salt length. Three special values are supported: digest sets the salt
length to the digest length, max sets the salt length to the maximum permissible value. When verifying auto
causes the salt length to be automatically determined based on the PSS block structure.
rsa_mgf1_md:digest
For PSS and OAEP padding sets the MGF1 digest. If the MGF1 digest is not explicitly set in PSS mode then the
signing digest is used.
rsa_oaep_md:digest
Sets the digest used for the OAEP hash function. If not explicitly set then SHA256 is used.
rsa_pkcs1_implicit_rejection:flag
Disables (when set to 0) or enables (when set to 1) the use of implicit rejection with PKCS#1 v1.5 decryption.
When enabled (the default), as a protection against Bleichenbacher attack, the library will generate a
deterministic random plaintext that it will return to the caller in case of padding check failure. When
disabled, it's the callers' responsibility to handle the returned errors in a side-channel free manner.
RSA-PSS ALGORITHM
The RSA-PSS algorithm is a restricted version of the RSA algorithm which only supports the sign and verify operations
with PSS padding. The following additional -pkeyopt values are supported:
rsa_padding_mode:mode, rsa_pss_saltlen:len, rsa_mgf1_md:digest
These have the same meaning as the RSA algorithm with some additional restrictions. The padding mode can only be
set to pss which is the default value.
If the key has parameter restrictions then the digest, MGF1 digest and salt length are set to the values
specified in the parameters. The digest and MG cannot be changed and the salt length cannot be set to a value
less than the minimum restriction.
DSA ALGORITHM
The DSA algorithm supports signing and verification operations only. Currently there are no additional -pkeyopt
options other than digest. The SHA256 digest is assumed by default.
DH ALGORITHM
The DH algorithm only supports the derivation operation and no additional -pkeyopt options.
EC ALGORITHM
The EC algorithm supports sign, verify and derive operations. The sign and verify operations use ECDSA and derive
uses ECDH. SHA256 is assumed by default for the -pkeyopt digest option.
X25519 AND X448 ALGORITHMS
The X25519 and X448 algorithms support key derivation only. Currently there are no additional options.
SLH-DSA ALGORITHMS
The SLH-DSA algorithms (SLH-DSA-SHA2-128s, SLH-DSA-SHA2-128f, SLH-DSA-SHA2-192s, SLH-DSA-SHA2-192f,
SLH-DSA-SHA2-256s, SLH-DSA-SHA2-256f) are post-quantum signature algorithms. When using SLH-DSA with pkeyutl, the
following options are available:
-sign
Sign the input data using an SLH-DSA private key. For example:
$ openssl pkeyutl -sign -in file.txt -inkey slhdsa.pem -out sig
-verify
Verify the signature using an SLH-DSA public key. For example:
$ openssl pkeyutl -verify -in file.txt -inkey slhdsa.pem -sigfile sig
See EVP_PKEY-SLH-DSA(7) and EVP_SIGNATURE-SLH-DSA(7) for additional details about the SLH-DSA algorithm and its
implementation.
ML-DSA-44, ML-DSA-65 AND ML-DSA-87 ALGORITHMS
The ML-DSA algorithms are post-quantum signature algorithms that support signing and verification of "raw" messages.
No preliminary hashing is performed. When using ML-DSA with pkeyutl, the following options are available:
-sign
Sign the input data using an ML-DSA private key. For example:
$ openssl pkeyutl -sign -in file.txt -inkey mldsa65.pem -out sig
-verify
Verify the signature using an ML-DSA public key. For example:
$ openssl pkeyutl -verify -in file.txt -inkey mldsa65.pem -sigfile sig
-pkeyopt opt:value
Additional options for ML-DSA signing and verification:
message-encoding:value
Specifies the message encoding mode used for signing. This controls how the input message is processed before
signing. Valid values are described in EVP_SIGNATURE-ML-DSA(7). For example:
$ openssl pkeyutl -sign -in file.txt -inkey mldsa65.pem -out sig -pkeyopt message-encoding:1
test-entropy:value
Specifies a test entropy value for deterministic signing. For example:
$ openssl pkeyutl -sign -in file.txt -inkey mldsa65.pem -out sig -pkeyopt test-entropy:abcdefghijklmnopqrstuvwxyz012345
hextest-entropy:value
Specifies a test entropy value in hex format. For example:
$ openssl pkeyutl -sign -in file.txt -inkey mldsa65.pem -out sig -pkeyopt hextest-entropy:000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f
deterministic:value
Enables deterministic signing. For example:
$ openssl pkeyutl -sign -in file.txt -inkey mldsa65.pem -out sig -pkeyopt deterministic:1
mu:value
Specifies the mu parameter. For example:
$ echo -n "0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef" >file.txt
$ openssl pkeyutl -sign -in file.txt -inkey mldsa65.pem -out sig -pkeyopt mu:1
context-string:string
Specifies a context string for both signing and verification operations. The context string must be the same for
verification to succeed. For example:
$ openssl pkeyutl -sign -in file.txt -inkey mldsa65.pem -out sig -pkeyopt context-string:mycontext
$ openssl pkeyutl -verify -in file.txt -inkey mldsa65.pem -sigfile sig -pkeyopt context-string:mycontext
hexcontext-string:string
Specifies a context string in hex format, allowing binary control values. For example:
$ openssl pkeyutl -sign -in file.txt -inkey mldsa65.pem -out sig -pkeyopt hexcontext-string:6d79636f6e74657874
The signing operation supports a deterministic:bool option, with bool set to 1 if a deterministic signature is to be
generated with a fixed all zero random input. By default, or if the bool is 0 a random entropy value is used. A
deterministic result can also be obtained by specifying an explicit entropy value via the hextest-entropy:value
parameter. Deterministic ML-DSA signing should only be used in tests.
See EVP_SIGNATURE-ML-DSA(7) for additional details about the ML-DSA algorithms and their implementation.
ML-KEM-512, ML-KEM-768 AND ML-KEM-1024 ALGORITHMS
The ML-KEM algorithms support encapsulation and decapsulation only. The encapsulation operation supports a
hexikme:entropy option, with entropy the 64 hexadecimal digit encoding of a 32-byte value. This should only be used
in tests, known or leaked values of the option may compromise the generated shared secret.
See EVP_KEM-ML-KEM(7) for additional detail.
ED25519 AND ED448 ALGORITHMS
These algorithms only support signing and verifying. OpenSSL only implements the "pure" variants of these algorithms
so raw data can be passed directly to them without hashing them first. OpenSSL only supports "oneshot" operation with
these algorithms. This means that the entire file to be signed/verified must be read into memory before processing
it. Signing or Verifying very large files should be avoided. Additionally the size of the file must be known for this
to work. If the size of the file cannot be determined (for example if the input is stdin) then the sign or verify
operation will fail.
SM2
The SM2 algorithm supports sign, verify, encrypt and decrypt operations. For the sign and verify operations, SM2
requires an Distinguishing ID string to be passed in. The following -pkeyopt value is supported:
distid:string
This sets the ID string used in SM2 sign or verify operations. While verifying an SM2 signature, the ID string
must be the same one used when signing the data. Otherwise the verification will fail.
hexdistid:hex_string
This sets the ID string used in SM2 sign or verify operations. While verifying an SM2 signature, the ID string
must be the same one used when signing the data. Otherwise the verification will fail. The ID string provided
with this option should be a valid hexadecimal value.
EXAMPLES
Sign some data using a private key:
openssl pkeyutl -sign -in file -inkey key.pem -out sig
Recover the signed data (e.g. if an RSA key is used):
openssl pkeyutl -verifyrecover -in sig -inkey key.pem
Verify the signature (e.g. a DSA key):
openssl pkeyutl -verify -in file -sigfile sig -inkey key.pem
Sign data using a message digest value (this is currently only valid for RSA):
openssl pkeyutl -sign -in file -inkey key.pem -out sig -pkeyopt digest:sha256
Derive a shared secret value:
openssl pkeyutl -derive -inkey key.pem -peerkey pubkey.pem -out secret
Hexdump 48 bytes of TLS1 PRF using digest SHA256 and shared secret and seed consisting of the single byte 0xFF:
openssl pkeyutl -kdf TLS1-PRF -kdflen 48 -pkeyopt md:SHA256 \
-pkeyopt hexsecret:ff -pkeyopt hexseed:ff -hexdump
Derive a key using scrypt where the password is read from command line:
openssl pkeyutl -kdf scrypt -kdflen 16 -pkeyopt_passin pass \
-pkeyopt hexsalt:aabbcc -pkeyopt N:16384 -pkeyopt r:8 -pkeyopt p:1
Derive using the same algorithm, but read key from environment variable MYPASS:
openssl pkeyutl -kdf scrypt -kdflen 16 -pkeyopt_passin pass:env:MYPASS \
-pkeyopt hexsalt:aabbcc -pkeyopt N:16384 -pkeyopt r:8 -pkeyopt p:1
Sign some data using an SM2(7) private key and a specific ID:
openssl pkeyutl -sign -in file -inkey sm2.key -out sig -rawin -digest sm3 \
-pkeyopt distid:someid
Verify some data using an SM2(7) certificate and a specific ID:
openssl pkeyutl -verify -certin -in file -inkey sm2.cert -sigfile sig \
-rawin -digest sm3 -pkeyopt distid:someid
Decrypt some data using a private key with OAEP padding using SHA256:
openssl pkeyutl -decrypt -in file -inkey key.pem -out secret \
-pkeyopt rsa_padding_mode:oaep -pkeyopt rsa_oaep_md:sha256
Create an ML-DSA key pair and sign data with a specific context string:
$ openssl genpkey -algorithm ML-DSA-65 -out mldsa65.pem
$ openssl pkeyutl -sign -in file.txt -inkey mldsa65.pem -out sig -pkeyopt context-string:example
Verify a signature using ML-DSA with the same context string:
$ openssl pkeyutl -verify -in file.txt -inkey mldsa65.pem -sigfile sig -pkeyopt context-string:example
Generate an ML-KEM key pair and use it for encapsulation:
$ openssl genpkey -algorithm ML-KEM-768 -out mlkem768.pem
$ openssl pkey -in mlkem768.pem -pubout -out mlkem768_pub.pem
$ openssl pkeyutl -encap -inkey mlkem768_pub.pem -pubin -out ciphertext -secret shared_secret.bin
Decapsulate a shared secret using an ML-KEM private key:
$ openssl pkeyutl -decap -inkey mlkem768.pem -in ciphertext -secret decapsulated_secret.bin
Create an SLH-DSA key pair and sign data:
$ openssl genpkey -algorithm SLH-DSA-SHA2-128s -out slh-dsa.pem
$ openssl pkeyutl -sign -in file.txt -inkey slh-dsa.pem -out sig
Verify a signature using SLH-DSA:
$ openssl pkeyutl -verify -in file.txt -inkey slh-dsa.pem -sigfile sig
SEE ALSO
openssl(1), openssl-genpkey(1), openssl-pkey(1), openssl-rsautl(1) openssl-dgst(1), openssl-rsa(1),
openssl-genrsa(1), openssl-kdf(1) EVP_PKEY_CTX_set_hkdf_md(3), EVP_PKEY_CTX_set_tls1_prf_md(3),
HISTORY
Since OpenSSL 3.5, the -digest option implies -rawin, and these two options are no longer required when signing or
verifying with an Ed25519 or Ed448 key.
Also since OpenSSL 3.5, the -kemop option is no longer required for any of the supported algorithms, the only
supported mode is now the default.
The -engine option was deprecated in OpenSSL 3.0.
COPYRIGHT
Copyright 2006-2025 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the Apache License 2.0 (the "License"). You may not use this file except in compliance with the
License. You can obtain a copy in the file LICENSE in the source distribution or at
.
3.5.5 2026-01-27 OPENSSL-PKEYUTL(1SSL)